Method and apparatus for timing advance adjustment

ABSTRACT

This application provides a method and an apparatus for determining an effective time of a timing advance (TA). The method includes: determining a first subcarrier spacing from M subcarrier spacings, where the M subcarrier spacings are subcarrier spacings of L carriers used by a terminal device, and L≥M≥2; and determining an effective time of a timing advance (TA) of each of the L carriers based on the first subcarrier spacing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2019/086459, filed on May 10, 2019, which claims priority toChinese Patent Application No. 201810450341.7, filed on May 11, 2018 andclaims priority to Chinese Patent Application No. 201810820209.0, filedon Jul. 24, 2018. The disclosures of the aforementioned applications arehereby incorporated by reference in their entireties.

TECHNICAL FIELD

This application relates to the communications field, and morespecifically, to a method and an apparatus for determining an effectivemoment of a timing advance (TA).

BACKGROUND

To ensure orthogonality of uplink transmission and avoid intra-cellinterference, uplink signals from different terminal devices (forexample: user equipment, UE) are required to arrive at a network deviceat substantially aligned times. Therefore, the network device sends atiming advance (TA) to the terminal device, and the terminal deviceadjusts, based on the received TA, a time for sending the uplink signal,to implement uplink timing synchronization between the terminal deviceand the network device.

There is a specific time interval between a start time of receiving adownlink signal by the terminal device and a time of transmitting anuplink signal by the terminal device, and different terminal deviceshave different time intervals. In a process of adjusting the TA, theterminal device first receives a TA adjustment command sent by thenetwork device, and after a period of time, the terminal device appliesa new TA until a new TA adjustment command is received. The terminaldevice may control a TA effective time by controlling the time interval.

Currently, because uplink (UL) resources have different subcarrierspacings (SCS), time intervals are different. Consequently, TA effectivetimes of different UL carriers in a same timing advance group (TAG) aredifferent. In addition, different TA effective times increaseimplementation complexity of the terminal device.

SUMMARY

This application provides a method and an apparatus for determining aneffective moment of a timing advance (TA), to ensure uplink timingsynchronization between a terminal device and a network device.

According to a first aspect, a communication method is provided,including: determining a first subcarrier spacing from M subcarrierspacings, where the M subcarrier spacings are subcarrier spacingscorresponding to L carriers used by a terminal device, and L≥M≥2; anddetermining an effective moment of a timing advance (TA) of each of theL carriers based on the first subcarrier spacing.

A network device sends configuration information to the terminal device,to indicate an uplink subcarrier spacing, and sends a TA adjustmentcommand to the terminal device. The terminal device receives the TAadjustment command sent by the network device, where the TA adjustmentcommand includes a TA adjustment amount; and the terminal devicedetermines a new timing advance based on a current timing advance (TA)and the TA adjustment amount.

A base station determines a timing advance of each user equipment (UE)by measuring an uplink signal transmitted by the UE, and notifies the UEof the timing advance. For a terminal device, there is a specific timeinterval from a moment at which the terminal device receives a downlinksignal to a moment at which a TA starts to take effect. The timeinterval is referred to as a first time interval N in this application.The first time interval N may be defined as K slots (slots), and totalduration of the first time interval N includes four parts of durationshown in FIG. 4: N₁, N₂, L₂, and TA_(max).

A mobile communications system supports a plurality of subcarrierspacings (for example, the subcarrier spacings are applicable todifferent service types or working frequencies), and symbols ofdifferent subcarrier spacings respectively correspond to differentcyclic prefix (CP) lengths. Correspondingly, different subcarrierspacings correspond to different anti-latency influence performance.Therefore, the UE uses different timing advances in different scenarios,so that diversified requirements of a 5G mobile communications systemfor uplink synchronization can be met. Currently, in carrier resources,different subcarrier spacings include 15 kHz, 30 kHz, 60 kHz, and 120kHz, and may have more possibilities in the future. It should beunderstood that this application includes these subcarrier spacings butis not limited thereto.

In a case of different UL subcarrier spacings, absolute lengths of N₁,N₂, and TA_(max) are different. Consequently, TA effective times ofdifferent UL carriers in a same TAG are different. Different TAeffective times increase implementation complexity of the terminaldevice, and do not conform to a definition of a same TAG.

An embodiment of this application provides a method for determining a TAeffective time. A time interval N before the TA effective time isdetermined, and it is ensured that for a same terminal device, the timeinterval N is consistent when a plurality of UL subcarrier spacings areincluded. In this way, in a same TAG, TA effective times of the terminaldevice are consistent, so that uplink timing synchronization between theterminal device and the network device can be ensured.

Optionally, the terminal device determines the first subcarrier spacingfrom the M subcarrier spacings. Specific methods for determining thefirst subcarrier spacing are listed as follows:

Case 1

For the L uplink (UL) carriers, N₁ and N₂ are determined with referenceto a minimum UL subcarrier spacing. For example, if L=2 uplink (UL)carriers are configured for the UE, and subcarrier spacings arerespectively 15 kHz and 30 kHz, N₁ and N₂ are calculated based on 15kHz.

Case 2

For the L uplink (UL) carriers, N₁ and N₂ are determined with referenceto a maximum UL subcarrier spacing. For example, if L=2 uplink (UL)carriers are configured for the UE, and subcarrier spacings arerespectively 15 kHz and 30 kHz, N₁ and N₂ are calculated based on 30kHz.

Case 3

For the L uplink (UL) carriers, TA_(max) is determined with reference toa minimum UL subcarrier spacing. For example, if L=2 uplink (UL)carriers are configured for the UE, and subcarrier spacings arerespectively 15 kHz and 30 kHz, TA_(max) is calculated based on 15 kHz.

Case 4

For the L uplink (UL) carriers, TA_(max) is determined with reference toa maximum UL subcarrier spacing. For example, if L=2 uplink (UL)carriers are configured for the UE, and subcarrier spacings arerespectively 15 kHz and 30 kHz, TA_(max) is calculated based on 30 kHz.

Case 5

For the L uplink (UL) carriers, N₁, N₂, and TA_(max) are determined withreference to a minimum UL subcarrier spacing. For example, if L=2 uplink(UL) carriers are configured for the UE, and subcarrier spacings arerespectively 15 kHz and 30 kHz, a time interval is calculated based on15 kHz.

Case 6

For the L uplink (UL) carriers, N₁, N₂, and TA_(max) are determined withreference to a maximum UL subcarrier spacing. For example, if L=2 uplink(UL) carriers are configured for the UE, and subcarrier spacings arerespectively 15 kHz and 30 kHz, a time interval is calculated based on30 kHz.

Case 7

For the L uplink (UL) carriers, N₁ and N₂ are determined with referenceto a minimum UL subcarrier spacing, and TA_(max) is determined withreference to a maximum UL subcarrier spacing.

For example, if L=2 uplink (UL) carriers are configured for the UE, andsubcarrier spacings are respectively 15 kHz and 30 kHz, duringcalculation of a time interval, N₁ and N₂ are determined based on 15kHz, and TA_(max) is determined based on 30 kHz.

Case 8

For the L uplink (UL) carriers, N₁ and N₂ are determined with referenceto a maximum UL subcarrier spacing, and TA_(max) is determined withreference to a minimum UL subcarrier spacing.

For example, if L=2 uplink (UL) carriers are configured for the UE, andsubcarrier spacings are respectively 15 kHz and 30 kHz, duringcalculation of a time interval, N₁ and N₂ are determined based on 30kHz, and TA_(max) is determined based on 15 kHz.

Case 9

For the L uplink (UL) carriers, N₁ and N₂ are determined with referenceto a minimum UL subcarrier spacing, and TA_(max) is determined withreference to a minimum value in a subcarrier spacing in the uplink (UL)carriers and a subcarrier spacing of a carrier resource used to transmitan Msg3, that is, μ=min(Msg3 SCS, UL SCS).

Case 10

For the L uplink (UL) carriers and subcarrier spacings of T messages 3(Msg3) in a random access process, N₁ and N₂ are determined withreference to a minimum UL subcarrier spacing, and TA_(max) is determinedwith reference to a maximum/minimum subcarrier spacing, that is,μ=min(max(Msg3 SCSs), UL SCS), or μ=min(min(Msg3 SCSs), UL SCS).

For example, if the base station configures random access resources onthe UL and an SUL, and subcarrier spacings of the Msg3 of the basestation are respectively 15 kHz or 30 kHz, μ corresponding to TA_(max)is determined with reference to the minimum subcarrier spacing 15 kHz,or μ is determined with reference to the maximum subcarrier spacing 30kHz.

Optionally, the UL SCSs of L uplink (UL) carriers may be SCSs of allbandwidth pails (BWPs) in an active state, or subcarrier spacings of aplurality of BWPs configured for the terminal device, or subcarrierspacings of all BWPs.

It should be understood that, in a random access process, a subcarrierspacing of an uplink carrier resource for transmitting the Msg3 may be15 kHz. After the random access process is completed, a subcarrierspacing for transmitting an uplink resource may be reconfigured. Forexample, a subcarrier spacing of an allocated carrier resource may be 30kHz or 60 kHz. Therefore, in consideration of impact of random access,impact of the subcarrier spacing of the Msg3 is considered in a processof determining TA_(max) herein. In addition, because a plurality ofuplink carriers may each have a corresponding random access resource,the uplink carriers may correspond to different subcarrier spacings ofthe message 3. For example, an uplink (UL) carrier and a supplementaryuplink (supplementary UL, SUL) carrier are configured for the UE. Themessage 3 may have two subcarrier spacings, for example, 15 kHz and 30kHz respectively. Therefore, in the process of determining TA_(max),impact of a plurality of subcarrier spacings of the Msg3 is also takeninto consideration.

For example, an uplink (UL) subcarrier spacing used by the UE isdifferent from that of the Msg3. To support a maximum coverage range,TA_(max) needs to be a minimum value in the subcarrier spacing of theMsg3 and the configured UL subcarrier spacing (SCS). For example, if L=2uplink (UL) carriers are configured for the UE, subcarrier spacings arerespectively 60 kHz and 30 kHz, and in a random access process, asubcarrier spacing (SCS) of a carrier resource for transmitting the Msg3is 15 kHz, during calculation of a time interval, N₁ and N₂ aredetermined based on 30 kHz, and TA_(max) is determined based on 15 kHz.

Ten possible cases of the first subcarrier spacing used for determiningN₁, N₂, and TA_(max) are listed above. It should be understood that theforegoing cases are merely examples instead of limitations. In variousprocesses of determining the first subcarrier spacing, there may be morecases of combining the first subcarrier spacings used for determiningN₁, N₂, and TA_(max). This application includes these cases but is notlimited thereto.

Optionally, in a process of determining the first subcarrier spacing,the terminal device may set a first threshold, and determine the firstthreshold as the first subcarrier spacing, to participate in subsequentdetermining of the effective moment of the TA.

Optionally, the foregoing method provided in this application mayalternatively be used in combination with the prior art. For example, aminimum value is obtained from the determined first subcarrier spacingof the uplink carrier resource and a subcarrier spacing of a downlinkcarrier resource, to obtain a subcarrier spacing. Details are notdescribed herein. It should be understood that this application includesthese but is not limited thereto.

With reference to the first aspect, in some implementations of the firstaspect, the determining an effective moment of a timing advance (TA) ofeach of the L carriers based on the first subcarrier spacing includes:determining, based on the first subcarrier spacing, a first timeinterval corresponding to a first carrier in the L carriers, where thefirst time interval is a time interval between a receiving moment of adownlink signal and an effective moment of a TA; and determining theeffective moment of the timing advance (TA) of each of the L carriersbased on the first time interval.

Optionally, the terminal device determines, based on the firstsubcarrier spacing, the first time interval corresponding to the firstcarrier in the L carriers, where the first time interval is the timeinterval between the receiving moment of the downlink signal and theeffective moment of the TA; and then determines the effective moment ofthe timing advance (TA) of each of the L carriers based on the firsttime interval.

For example, when a subcarrier spacing of a downlink DL is 15 kHz, asubcarrier spacing of an uplink (UL) carrier is 30 kHz, andμ=min(μ_(DL), μ_(UL))=min(15 kHz, 30 kHz)=15 kHz, it is learnedaccording to Formula (1) that the first time intervalN=ceil(N₁+N₂+L₂+TA_(max))=ceil(13 symbols+10 symbols+0.5 ms+2ms)=ceil(58 symbols)=5 ms.

With reference to the first aspect and the foregoing implementations, insome possible implementations, the first time interval includes one ormore of first duration, second duration, and third duration, and thedetermining, based on the first subcarrier spacing, a first timeinterval corresponding to a first carrier in the L carriers includes:

determining the first duration based on the first subcarrier spacing,where the first duration is duration required for processing a downlinksignal; and/or

determining the second duration based on the first subcarrier spacing,where the second duration is duration required for preparing an uplinksignal; and/or

determining the third duration based on the first subcarrier spacing,where the third duration is maximum duration that is allowed to beindicated by a 12-bit or 6-bit timing advance command (TAC) when thethird duration is determined based on the first subcarrier spacing.

Optionally, the first time interval may be determined with reference toa maximum subcarrier spacing or a minimum subcarrier spacing. Forexample, if the maximum subcarrier spacing is 30 kHz, and the minimumsubcarrier spacing is 15 kHz, the first time interval determinedaccording to the foregoing method is 5 ms. When the first time intervalis determined with reference to the subcarrier spacing of 15 kHz, 5 msis equivalent to 5 slots. To be specific, for an uplink carrier of 15kHz, a TA is applied starting from a sixth slot. When the first timeinterval is determined with reference to the subcarrier spacing of 30kHz, 5 ms is equivalent to 10 slots. To be specific, for an uplinkcarrier of 30 kHz, a TA is applied starting from an eleventh slot.

Optionally, when the first time interval is determined with reference tothe maximum subcarrier spacing, for a small subcarrier spacing, thefirst time interval cannot be integral slots, and a rounding upoperation needs to be performed on the first time interval. The roundingup operation means selecting a value that is greater than the originalfirst time interval and that is a minimum integer multiple of slotduration corresponding to the minimum subcarrier spacing. For example,the first time interval determined according to the foregoing method is2.5 ms, and includes two carriers (15 kHz and 30 kHz). Because 2.5 ms isnot an integer multiple of a slot corresponding to the subcarrierspacing of 15 kHz, the first time interval of 2.5 ms needs to be roundedup first based on a step of 15 kHz, that is, 3 ms. 3 ms corresponds to 3slots (15 kHz) and 6 slots (30 kHz). Therefore, for the subcarrierspacing of 15 kHz, a new TA is applied starting from a fourth slot, andfor the subcarrier spacing of 30 kHz, a new TA is applied starting froma seventh slot.

It should be understood that 12 bits herein are merely an exampleinstead of a limitation, and another possible value less than 12 bits,for example, 6 bits, may also be used.

It should be understood that the duration required for processing adownlink signal is related to a downlink signal configuration such as ademodulation reference signal configuration, and/or a downlink signalsubcarrier spacing, and/or a UE processing capability. It should beunderstood that the duration required for preparing an uplink signal isrelated to an uplink signal subcarrier spacing and/or a UE processingcapability.

It should be understood that in the listed processes of determining thefirst time interval herein, a sum may be obtained according to Formula(i) by separately determining duration of N₁, N₂, L₂, and TA_(max), toobtain the first time interval N. Alternatively, in this embodiment ofthis application, only duration of one or more of N₁, N₂, L₂, andTA_(max) may be determined. In a technology development process, it ispossible that only duration of at least one of N₁, N₂, L₂, and TA_(max)needs to be determined, and the first time interval N may be obtained byusing a specific relationship. Herein, a method for determining durationof any one or more of N₁, N₂, L₂, and TA_(max) by using the methodprovided in this application falls within the protection scope of thisapplication.

With reference to the first aspect and the foregoing implementations, insome possible implementations, when at least two of the L carriers areused for a random access process, and a carrier used to transmit amessage Msg3 includes at least two subcarrier spacings, before thedetermining the third duration based on the first subcarrier spacing,the method further includes: determining the first subcarrier spacingbased on the at least two subcarrier spacings.

With reference to the first aspect and the foregoing implementations, insome possible implementations, the first time interval further includesfourth duration, and the fourth duration is duration determined by theterminal device based on a cell reuse mode; and/or the fourth durationis duration determined by the terminal device based on a frequency rangewithin which the terminal device or a network device works.

With reference to the first aspect and the foregoing implementations, insome possible implementations, the method further includes: determininga first mapping relationship, where the first mapping relationshipincludes a one-to-one mapping relationship between a plurality ofsubcarrier spacings and a plurality of pieces of duration. Thedetermining an effective moment of a timing advance (TA) of each of theL carriers based on the first subcarrier spacing includes: determining,based on the first mapping relationship, a first time intervalcorresponding to the first subcarrier spacing; and determining theeffective moment of the timing advance (TA) of each of the L carriersbased on the first time interval. Specifically, the terminal devicelearns, based on a network device configuration, subcarrier spacings ofall uplink (UL) carriers in a TAG; and then, receives a MAC-CE thatincludes a TA adjustment command and that is delivered by the networkdevice, and determines an effective moment of a TA; and then, can use anew TA included in the MAC-CE.

After receiving the MAC-CE that includes the TA adjustment command, theterminal device determines the first time interval based on a minimum ormaximum uplink subcarrier spacing in a same TAG. For example, theterminal device may determine the first time interval based on a presetfunction.

With reference to the first aspect and the foregoing implementations, insome possible implementations, the first subcarrier spacing is a minimumsubcarrier spacing among the M subcarrier spacings, or the firstsubcarrier spacing is a maximum subcarrier spacing among the Msubcarrier spacings.

It should be understood that the first subcarrier spacing may bedetermined based on one or more of a maximum/minimum value among alluplink subcarrier spacings, or a maximum/minimum value among subcarrierspacings of all bandwidth parts in an active state, or a maximum/minimumvalue among subcarrier spacings of a plurality of BWPs configured forthe terminal device, or a maximum/minimum value among subcarrierspacings of all BWPs. Alternatively, the first subcarrier spacing may befixedly set to a subcarrier spacing, for example, for a low frequency (aworking frequency that is less than or equal to 6 GHz), the firstsubcarrier spacing may be fixedly set to 15 kHz.

Optionally, in a process of determining the first subcarrier spacing,the terminal device may set a first threshold, and determine the firstthreshold as the first subcarrier spacing, to participate in subsequentdetermining of the effective moment of the TA.

With reference to the first aspect and the foregoing implementations, insome possible implementations, after the determining an effective momentof a timing advance (TA) of each of the L carriers based on the firstsubcarrier spacing, the method further includes: sending uplinkinformation based on the timing advance (TA).

The foregoing describes a detailed process in which the terminal devicedetermines the effective moment of the timing advance (TA). Afterdetermining the first time interval N, the terminal device can determinethe effective moment of the TA by adding duration represented by thefirst time interval N to the receiving moment of the downlink signal.After determining the effective moment of the timing advance (TA) ofeach of the L carriers, the terminal device may send the uplinkinformation based on the timing advance (TA).

According to a second aspect, a communications apparatus is provided,including: a determining unit, configured to determine a firstsubcarrier spacing from M subcarrier spacings, where the M subcarrierspacings are subcarrier spacings corresponding to L carriers used by aterminal device, and L≥M≥2; and the determining unit is furtherconfigured to determine an effective moment of a timing advance (TA) ofeach of the L carriers based on the first subcarrier spacing.

With reference to the second aspect, in some possible implementations,the determining unit is further configured to: determine, based on thefirst subcarrier spacing, a first time interval corresponding to a firstcarrier in the L carriers, where the first time interval is a timeinterval between a receiving moment of a downlink signal and aneffective moment of a TA; and determine the effective moment of thetiming advance (TA) of each of the L carriers based on the first timeinterval.

With reference to the second aspect and the foregoing implementations,in some possible implementations, the first time interval includes oneor more of first duration, second duration, and third duration, and thedetermining unit is further configured to: determine the first durationbased on the first subcarrier spacing, where the first duration isduration required for processing a downlink signal; and/or determine thesecond duration based on the first subcarrier spacing, where the secondduration is duration required for preparing an uplink signal; and/ordetermine the third duration based on the first subcarrier spacing,where the third duration is maximum duration that is allowed to beindicated by a 12-bit or 6-bit timing advance command (TAC) when thethird duration is determined based on the first subcarrier spacing.

With reference to the second aspect and the foregoing implementations,in some possible implementations, when at least two of the L carriersare used for a random access process, and a carrier used to transmit amessage Msg3 includes at least two subcarrier spacings, beforedetermining the third duration based on the first subcarrier spacing,the determining unit is further configured to determine the firstsubcarrier spacing based on the at least two subcarrier spacings.

With reference to the second aspect and the foregoing possibleimplementations, in some possible implementations, the first timeinterval further includes fourth duration, and the fourth duration isduration determined by the terminal device based on a cell reuse mode;and/or the fourth duration is duration determined by the terminal devicebased on a frequency range within which the terminal device or a networkdevice works.

With reference to the second aspect and the foregoing implementations,in some possible implementations, the determining unit is furtherconfigured to: determine a first mapping relationship, where the firstmapping relationship includes a one-to-one mapping relationship betweena plurality of subcarrier spacings and a plurality of pieces ofduration; determine, based on the first mapping relationship, a firsttime interval corresponding to the first subcarrier spacing; anddetermine the effective moment of the timing advance (TA) of each of theL carriers based on the first time interval.

With reference to the second aspect and the foregoing implementations,in some possible implementations, the first subcarrier spacing is aminimum subcarrier spacing among the M subcarrier spacings, or the firstsubcarrier spacing is a maximum subcarrier spacing among the Msubcarrier spacings.

With reference to the second aspect and the foregoing implementations,in some possible implementations, the apparatus further includes asending unit, configured to send uplink information based on the timingadvance (TA).

According to a third aspect, a communications apparatus is provided. Thecommunications apparatus has a function of implementing behaviors of theterminal device in any one of the first aspect and the possibleimplementation method designs of the first aspect. The function may beimplemented by using hardware, or may be implemented by executingcorresponding software by hardware. The hardware or the softwareincludes one or more modules corresponding to the function. The modulemay be software and/or hardware.

With reference to the third aspect, in some possible implementations, astructure of the communications apparatus includes a memory and aprocessor. The processor is configured to be coupled to the memory toexecute an instruction in the memory, to implement the method in any oneof the first aspect and the possible implementation method designs ofthe first aspect. The memory is configured to store a programinstruction and data.

According to a fourth aspect, a computer readable storage medium isprovided and is configured to store a computer program. The computerprogram includes an instruction that is used to execute the method inany one of the first aspect and the possible implementation methoddesigns of the first aspect.

According to a fifth aspect, a computer program product is provided. Thecomputer program product includes a computer program code, and when thecomputer program code runs on a computer, the computer performs thecommunication method in any one of the first aspect and the possibleimplementation method designs of the first aspect.

According to a sixth aspect, a chip system is provided. The chip systemincludes a processor, configured to support a network device inimplementing functions in the foregoing aspects, for example,generating, receiving, determining, sending, or processing data and/orinformation in the foregoing method. In a possible design, the chipsystem further includes a memory, and the memory is configured to storea program instruction and data that are necessary for a terminal device.The chip system may include a chip, or may include a chip and anotherdiscrete device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an example wireless communicationssystem according to an embodiment of this application;

FIG. 2 is a schematic diagram of interaction between a terminal deviceand a network device in a TA adjustment process;

FIG. 3 is a schematic diagram in which a terminal device sends uplinkinformation based on a timing advance (TA);

FIG. 4 is a schematic diagram of an example effective moment of a TAaccording to an embodiment of this application;

FIG. 5 is a schematic flowchart of a method for determining an effectivemoment of a TA according to an embodiment of this application;

FIG. 6 is a schematic block diagram of an example communicationsapparatus according to an embodiment of this application;

FIG. 7 is a schematic structural diagram of an example terminal deviceaccording to an embodiment of this application; and

FIG. 8 is a schematic structural diagram of another example terminaldevice according to an embodiment of this application.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The following describes technical solutions of this application withreference to the accompanying drawings.

Manners, cases, categories, and embodiment division in the embodimentsof this application are merely for ease of description, and should notconstitute a special limitation. Various manners, categories, cases, andfeatures in the embodiments may be combined, provided that they do notconflict with each other.

It should be noted that, in the embodiments of this application, a“protocol” may be a standard protocol in the communications field, forexample, may include an LTE protocol, an NR protocol, and a relatedprotocol applied to a future communications system. This applicationincludes these protocols but is not limited thereto.

It should be further noted that, in the embodiments of this application,“predefined” may be implemented by prestoring corresponding code or acorresponding table in a device (for example, a terminal device and anetwork device), or may be implemented in another manner that can beused to indicate related information. A specific implementation is notlimited in this application. For example, “predefined” may be “definedin a protocol”.

It should be further noted that, in the embodiments of this application,nouns “network” and “system” are usually used interchangeably, but aperson skilled in the art can understand their meanings. Information,signal, message, and channel may be used interchangeably sometimes. Itshould be noted that when differences therebetween are not emphasized,meanings expressed by information, signal, message, and channel areconsistent. “Of (of)”, and “corresponding” may be used interchangeablysometimes. It should be noted that when differences therebetween are notemphasized, meanings expressed by “of” and “corresponding” areconsistent.

It should be further noted that, in the embodiments of this application,“report” and “feed back” are usually used interchangeably, but a personskilled in the art can understand their meanings. For the terminaldevice, both reporting CSI and feeding back CSI may substantially besending CSI through a physical uplink channel. Therefore, in theembodiments of this application, when differences therebetween are notemphasized, meanings to be expressed by “report” and “feed back” areconsistent.

It should be further noted that the term “and/or” describes anassociation relationship between associated objects and denotes thatthree relationships may exist. For example, A and/or B may represent thefollowing three cases: Only A exists, both A and B exist, and only Bexists. The character “/” generally indicates an “or” relationshipbetween the associated objects.

The technical solutions of the embodiments of this application may beapplied to various communications systems, for example, a long termevolution (LTE) system, an LTE frequency division duplex (FDD) system,an LTE time division duplex (TDD) system, a 5th generation (5G) mobilecommunications system or a new radio (NR) communications system, and afuture mobile communications system.

For ease of understanding of the embodiments of this application, first,a communications system shown in FIG. 1 is used as an example todescribe in detail a communications system applicable to the embodimentsof this application. FIG. 1 is a schematic diagram of a wirelesscommunications system 100 applicable to an embodiment of thisapplication. As shown in FIG. 1, the wireless communications system 100may include one or more network devices, for example, a network device101 shown in FIG. 1. The wireless communications system 100 may furtherinclude one or more terminal devices, for example, a terminal device #1102 and a terminal device #2 103 shown in FIG. 1. The wirelesscommunications system 100 may support coordinated multipointtransmission/reception (CoMP). To be specific, a plurality of cells or aplurality of network devices may coordinate with each other toparticipate in data transmission of a terminal device or jointly receivedata sent by a terminal device; or a plurality of cells or a pluralityof network devices perform coordinated scheduling or coordinatedbeamforming. The plurality of cells may belong to a same network deviceor different network devices, and may be selected based on a channelgain or path loss, received signal strength, a signal receivinginstruction, or the like.

It should be understood that the network device in the wirelesscommunications system may be any device that has a wireless transceiverfunction or a chip that may be disposed in the device. The deviceincludes but is not limited to a base station, an evolved NodeB (eNB), ahome eNodeB, an access point (AP) in a wireless fidelity (WIFI) system,a wireless relay node, a wireless backhaul node, a transmission point(TP) or a transmission and reception point (TRP), and the like, or maybe a gNB in an NR system, or may be a component or a part of a devicethat forms a base station, such as a central unit (CU), a distributedunit (DU), or a baseband unit (BBU). It should be understood that, aspecific technology and a specific device form used by a wireless accessnetwork device are not limited in this embodiment of this application.In this application, the wireless access network device is referred toas a network device for short. If no special description is provided,all network devices in this application mean the wireless access networkdevice. In this application, the network device may be a network device,or may be a chip that is applied to a network device to implement awireless communication processing function.

In some deployments, the gNB may include a CU and a DU. The gNB mayfurther include a radio frequency unit (RFU). The CU implements somefunctions of the gNB, and the DU implements some functions of the gNB.For example, the CU implements functions of a radio resource control(RRC) layer and a packet data convergence protocol (PDCP) layer, and theDU implements functions of a radio link control (RLC) layer, a mediaaccess control (MAC) layer, and a physical (PHY) layer. Information ofthe RRC layer eventually becomes information of the PHY layer, or isconverted from information of the PHY layer. Therefore, in thisarchitecture, it may also be considered that higher layer signaling,such as RRC layer signaling or PDCP layer signaling, is sent by the DUor sent by the DU and the RU. It may be understood that the networkdevice may be a CU node, a DU node, or a device including a CU node anda DU node. In addition, the CU may be classified into a network devicein an access network RAN, or the CU may be classified into a networkdevice in a core network CN. This is not limited herein.

It should also be understood that the terminal device in the wirelesscommunications system may also be referred to as a terminal, userequipment (UE), a mobile station (MS), a mobile terminal (MT), or thelike. The terminal device in this embodiment of this application may bea mobile phone, a tablet computer, a computer with a wirelesstransceiver function, or may be a wireless terminal applied to scenariossuch as virtual reality (VR), augmented reality (AR), industrialcontrol, self driving, remote medical, a smart grid, transportationsafety, a smart city, and a smart home. In this application, theforegoing terminal device and the chip that can be applied to theterminal device are collectively referred to as a terminal device. Itshould be understood that a specific technology and a specific deviceform used by the terminal device are not limited in this embodiment ofthis application.

Optionally, in the communications system wo shown in FIG. 1, the networkdevice may be a serving network device. The serving network device maybe a network device that provides at least one service in an RRCconnection, non-access stratum (NAS) mobility management, and securityinput for the terminal device by using a wireless air interfaceprotocol. Optionally, the network device may be a coordinated networkdevice. The serving network device may send control signaling to theterminal device, and the coordinated network device may send data to theterminal device. Alternatively, the serving network device may sendcontrol signaling to the terminal device, and the servicing networkdevice and the coordinated network device may send data to the terminaldevice. Alternatively, both the serving network device and thecoordinated network device may send control signaling to the terminaldevice, and both the serving network device and the coordinated networkdevice may send data to the terminal device. Alternatively, thecoordinated network device may send control signaling to the terminaldevice, and at least one of the serving network device and thecoordinated network device may send data to the terminal device.Alternatively, the coordinated network device may send control signalingand data to the terminal device. This is not specially limited in thisembodiment of this application.

It should be understood that, FIG. 1 schematically shows the networkdevice and the terminal device merely for ease of understanding.However, this should not constitute any limitation on this application.The wireless communications system may further include more or fewernetwork devices, or may include more terminal devices. Network devicesthat communicate with different terminal devices may be a same networkdevice, or may be different network devices. Network devices thatcommunicate with different terminal devices may have a quantity the sameas or different from that of the terminal devices. This applicationincludes these but is not limited thereto.

The following uses a general interaction process between one terminaldevice and one network device as an example to describe this embodimentof this application in detail. The terminal device may be any terminaldevice in a wireless communications system that has a wirelessconnection relationship with one or more network devices. It may beunderstood that any terminal device in the wireless communicationssystem may implement wireless communication based on a same technicalsolution, and the following uses UE to represent a terminal device anduses gNB to identify a base station. This application includes these butis not limited thereto.

To facilitate understanding of the embodiments of this application, thefollowing briefly describes several nouns or terms in this application.

1. Timing advance group (TAG): A group of cells configured by a networkdevice by using radio resource control (RRC) signaling. To be specific,the network device configures a timing advance (TA) for a cell, and aTAG is formed when a plurality of cells have a same TA. For uplinkcarriers of the cells, a same uplink sending timing advance (TA) isused.

2. Timing Advance (TA)

A signal is transmitted in space with a latency, and the TA is used torepresent a distance between the terminal device and an antenna port ofthe network device. To ensure orthogonality of uplink transmissionprocesses of different terminal devices, and to ensure timesynchronization on a base station side, that is, to ensure that uplinksignals of different UEs arrive at the base station at an expected time,the communications system may use an uplink timing advance mechanism,and the UE sends uplink information based on a timing advance. For theUE, the timing advance is essentially a negative offset between a startmoment of a downlink subframe and a start moment of an uplink subframe.By properly controlling an offset of each UE, the base station maycontrol times at which uplink signals from different UEs arrive at thebase station. UE that is relatively close to the base station may senduplink information based on a relatively small timing advance. UE thatis relatively far away from the base station needs to send uplinkinformation based on a relatively large timing advance because a signalhas a relatively large transmission latency.

In a TAG, the network device configures a same timing advance (TA) forone or more cells, and the network device adjusts the TA based oninformation such as a location and a distance of the terminal device. Itshould be understood that the network device may perform adjustmentbased on a specific period, or the network device may perform adjustmentbased on information such as a location and a distance of the terminaldevice. This application includes these but is not limited thereto.

The terminal device receives a TA adjustment command sent by the networkdevice, and the TA adjustment command includes a TA adjustment amount.The terminal device determines a new timing advance based on a timingadvance (TA) of a current cell and the newly received TA adjustmentamount, and sends uplink information based on the new timing advance.

FIG. 2 is a schematic diagram of interaction between a terminal deviceand a network device in a TA adjustment process. As shown in FIG. 2, theTA adjustment process of the terminal device includes S201 to S205.

S201. The network device sends configuration information to the terminaldevice, to indicate an uplink subcarrier spacing.

S202. The network device sends a TA adjustment command to the terminaldevice.

S203. The terminal device receives the TA adjustment command sent by thenetwork device, and determines a time interval at which a TA takeseffect.

S204. After a period of time, apply a new TA, and apply the new TA in asubsequent slot, until a new TA adjustment command is received.

It should be understood that, in an actual TA adjustment process, theterminal device may perform some or all of the steps. This embodiment ofthis application is not limited thereto.

The base station notifies UE of a timing advance by using a timingadvance command (TAC), and different UEs correspond to different timingadvances. FIG. 3 is a schematic diagram in which UE sends uplinkinformation based on a timing advance. In FIG. 3, if a transmissiondistance of a signal between the UE and the base station is D, and thebase station expects to receive, at a moment T_(o), an uplink signalsent by the UE, the UE needs to send the uplink information at themoment T_(o)-T_(TA). TA represents a timing advance, a value of TA isD/c, and c represents a transmission rate of an electromagnetic wave.Because the UE has mobility, the transmission distance D of the signalbetween the UE and the base station also varies. Therefore, the UE needsto constantly adjust a value of the timing advance, to ensure that anerror between a moment at which the uplink signal arrives at the basestation and the moment at which the base station expects the uplinksignal to arrive at the base station is within an acceptable range.

The base station determines a timing advance of each UE by measuring anuplink signal transmitted by the UE. Theoretically, the base station maymeasure the timing advance based on any uplink signal sent by the UE,and the base station may notify the UE of the timing advance in thefollowing two manners.

Manner 1

In a random access process, the base station may notify the UE of thetiming advance (TA) by using a TAC field of a random access response(RAR). In this case, the base station determines the timing advance (TA)by measuring a preamble sequence sent by the UE. A size of the TAC fieldof the RAR may be, for example, 11 bits, and a range of a correspondingtiming advance coefficient is 0 to 1282. For random access, a value of acurrent timing advance is obtained by multiplying the timing advancecoefficient by 16T_(s), 16T_(s) is a time length, and in an LTE system,T_(s)=1/(15000×2048) seconds.

Manner 2

In a radio resource control connected mode, the base station may send atiming advance command media access control element (TAC MAC CE) to theUE.

The UE is in uplink synchronization with the base station in a randomaccess process, but a communication environment of the UE may vary withtime, and consequently a timing advance in the random access process isno longer applicable to a new communication environment. For example:

a transmission latency between UE that is moving at a high speed and thebase station may change greatly in a short period of time;

a current transmission path disappears and is switched to a newcommunication path, and a transmission latency of the new communicationpath changes greatly relative to the original communication path;

the UE has a crystal oscillator offset, and an offset accumulated in along period of time may cause an uplink timing error; and

UE movement causes Doppler frequency shift.

Therefore, the UE needs to constantly update the timing advance of theUE.

FIG. 4 is a schematic diagram of an effective moment of a TA. Currently,in NR, for a terminal device, there is a specific time interval from amoment at which the terminal device receives a downlink signal to amoment at which a TA starts to take effect. The time interval isreferred to as a first time interval N in this application. The firsttime interval N may be defined as K slots (slots), and total duration ofthe first time interval N includes four parts of duration shown in thefigure: N₁, N₂, L₂, and TA_(max) that may be represented as:N=ceil(N ₁ +N ₂ +L ₂ +TA _(max))  (1)

In Formula (1), ceil represents rounding up, and N₁, N₂, and TA_(max)are related to an uplink subcarrier spacing. N₁ represents time requiredby the terminal device to process a physical downlink shared channel(PDSCH), N₂ represents a latency of the terminal device in preparing aphysical uplink shared channel (PUSCH), L₂ represents a processinglatency of a media access control (MAC) layer of the terminal device,and TA_(max) is maximum duration that is allowed to be indicated by thetiming advance command (TAC). Specifically, for example, TA_(max) may bemaximum duration that is allowed to be indicated by a 12-bit TAC, ormaximum duration that is allowed to be indicated by a 6-bit TAC.

In a possible implementation, in addition to the listed N₁, N₂, L₂, andTA_(max), the first time interval further includes fourth duration, andthe fourth duration is duration determined by the terminal device basedon a cell reuse mode, or the fourth duration is duration determined bythe terminal device based on a frequency range within which the terminaldevice or the network device works. For example, the fourth duration isduration in which the terminal device performs handover in differentworking modes or working frequency bands, and a time at which theterminal device performs handover is denoted as N_(TA offset).

Optionally, duration represented by NTA offset and the maximum durationthat is allowed to be indicated by the 12-bit or 6-bit TAC may be addedand denoted as TA_(max) as a whole. For example, the maximum durationthat is allowed to be indicated by the TAC is denoted as N_(TA), andTA_(max)=N_(TA)+N_(TA offset). This is not limited in this application.

It should be understood that N_(TA offset) is the time at which theterminal device performs handover, for example, a time at which theterminal device performs uplink-downlink handover. Specifically, theuplink-downlink handover time N_(TA offset) may be related to a workingmode or working frequency band of a communications system, and values ofN_(TA offset) according to protocols may be, for example, shown inTable 1. FR1 represents a frequency band with a frequency less than 6GHz, and FR2 represents a frequency band with a frequency greater than 6GHz. The FR2 frequency band may be FDD, TDD, or both.

TABLE 1 Working mode and frequency band used for uplink transmissionN_(TA offset) (Unit: T_(C)) FDD FR₁ frequency band   0 TDD FR₁ frequencyband 39936 or 25600 FR₂ frequency band 13792

Alternatively, when a case in which LTE and NR coexist is taken intoconsideration, values of N_(TA offset) may be, for example, shown inTable 2. FR2 may be FDD, TDD, or both.

TABLE 2 Working mode and frequency band used for N_(TA offset) uplinktransmission (Unit: T_(C)) FDD FR₁ and TDD frequency bands do not 25600include a scenario in which LTE and NR coexist An FDD FR₁ frequency bandincludes the scenario   0 in which LTE and NR coexist A TDD FR₁frequency band includes the scenario 39936 in which LTE and NR coexistFR₂ frequency band 13792

The value of N_(TA offset) may be obtained by using one or more messagesin RRC signaling, downlink control information (DCI), and a media accesscontrol element (MAC-CE); or may be determined in an implicit manner,for example, the value of N_(TA offset is) implicitly indicated; or maybe predefined or preconfigured. It should be understood that a manner ofobtaining the value of N_(TA offset) is not limited in this application.

In addition, FR1 represents a scenario in which a working frequency isless than 6 GHz, and FR2 represents a scenario in which a workingfrequency is greater than or equal to 6 GHz. The unitT_(c)=1/(Δf_(max)·N_(f)), where Δf_(max)=480·10³ Hz, and N_(f)=4096.Optionally, Δf_(max)={15, 30, 60, 120, 240}10³, and is applied todifferent working frequency bands or subcarrier spacings. N_(f)={512,1024, 2048} is applied to different fast Fourier transform (FFT)sampling frequencies.

When a second uplink carrier is configured for the terminal device,N_(TA offset) may be determined based on a non-SUL carrier. The seconduplink carrier herein means a supplementary uplink (SUL) carrier.

It should be understood that, when N_(TA offset) is considered duringdetermining of TA_(max), Formula (1) may equivalently be represented as:N=ceil(N ₁ +N ₂ +L ₂ +N _(TA) +N _(TA offset))  (2)

In addition, it should be noted herein that the downlink signal in thisembodiment of this application may be a signal transmitted on a PDCCH,such as DCI or a demodulation reference signal (DMRS); or may be data orinformation transmitted on a PDSCH. The uplink signal may be data orinformation transmitted on a PUSCH, for example, uplink schedulinginformation, uplink control information (UCI), or feedback information.Specifically, the uplink signal is, for example, an acknowledgment(ACK)/a negative acknowledgment (NACK), or an uplink scheduling request(SR). It should be understood that this application includes these butis not limited thereto.

A 5G mobile communications system supports a plurality of subcarrierspacings (for example, the subcarrier spacings are applicable todifferent service types or working frequencies), and symbols ofdifferent subcarrier spacings respectively correspond to cyclic prefixes(CP) having different lengths. Correspondingly, different subcarrierspacings correspond to different anti-latency influence performance.Therefore, the UE uses different timing advances in different scenarios,so that diversified requirements of a 5G mobile communications systemfor uplink synchronization can be met. Currently, in carrier resources,different subcarrier spacings include 15 kHz, 30 kHz, 60 kHz, and 120kHz, and may have more possibilities in the future. It should beunderstood that this application includes these subcarrier spacings butis not limited thereto.

According to the protocol TS 38.214, a relationship between N₁ and anuplink subcarrier is also shown in Table 3 below. μ represents asubcarrier spacing, and 0, 1, 2, and 3 respectively correspond to 15kHz, 30 kHz, 60 kHz, and 120 kHz. PDSCH decoding time N₁ in Table 3 hastwo different reference cases. Because the TA adjustment command in thisapplication may be included in a MAC-CE and carried on a PDSCH, one caseis a decoding time of a PDSCH with an additional demodulation referencesignal (DMRS), and the other case is a decoding time of a PDSCH withoutan additional demodulation reference signal (DMRS). In this embodimentof this application, a relatively large decoding time, that is, thedecoding time of the PDSCH with the additional DMRS, is used as anexample for detailed description. It should be understood that thisembodiment of this application includes these but is not limitedthereto.

TABLE 3 PDSCH decoding time N₁ (unit: symbol) A DMRS of a PDSCH Anadditional DMRS μ is not added. of a PDSCH is added. 0  8 13 1 10 13 217 20 3 20 24

It should be understood that the symbol herein is a minimum unit of atime domain resource. In this embodiment of this application, a timelength of a symbol is not limited. For different subcarrier spacings, alength of a symbol may differ. The symbol may include an uplink symboland a downlink symbol. As an example instead of a limitation, the uplinksymbol may be referred to as a single carrier-frequency divisionmultiple access (SC-FDMA) symbol, an orthogonal frequency divisionmultiplexing (OFDM) symbol, or the like. The downlink symbol may bereferred to as an OFDM symbol or the like. This embodiment of thisapplication includes these but is not limited thereto.

A relationship between N₂ and an uplink subcarrier is also shown inTable 4 below. μ represents a subcarrier spacing, and 0, 1, 2, and 3respectively correspond to 15 kHz, 30 kHz, 60 kHz, and 120 kHz.

TABLE 4 PUSCH preparation time μ N₂ (unit: symbol) 0 10 1 12 2 23 3 36

A relationship between TA_(max) and an uplink subcarrier is also shownin Table 5 below. Time lengths of TA_(max) when subcarrier spacings arerespectively 15 kHz, 30 kHz, 60 kHz, and 120 kHz are listed.

TABLE 5 Subcarrier spacing TA_(max) (unit: kHz) (unit: ms)  15 2  30 1 60 0.5 120 0.25

In a process of determining an actual time interval N, the foregoing onetiming advance group (TAG) includes a plurality of cells, each cell mayinclude a plurality of terminal devices, and a plurality of uplinkcarrier resources are configured for each terminal device. In anexisting solution, a plurality of uplink resources in a timing advancegroup (TAG) have different subcarrier spacings (SCS). Specifically, whensubcarrier spacings of 15 kHz, 30 kHz, 60 kHz, and 120 kHz areconfigured for the terminal device, a time interval N can be determinedfor each subcarrier spacing.

For example, when the subcarrier spacing of 15 kHz is used as areference, the first time interval N=ceil(N₁+N₂+TA_(max))=ceil(13symbols+10 symbols+0.5 ms+2 ms)=ceil(58 symbols)=5 ms according toFormula (1). 0.5 ms=7 symbols, and 2 ms=28 symbols.

When the subcarrier spacing of 30 kHz is used as a reference, the firsttime interval N=ceil(N₁+N₂+L₂+TA_(max))=ceil(13=)+12 symbols+0.5 ms+1ms)=ceil(67 symbols)=2.5 ms according to Formula (1). 0.5 ms=14 symbols,and 1 ms=28 symbols.

It can be learned from the foregoing calculation process that in casesof different UL subcarrier spacings, absolute lengths of N₁, N₂, andTA_(max) are different. Consequently, TA effective times of different ULcarriers in a same TAG are different. Different TA effective timesincrease implementation complexity of the terminal device, and do notconform to a definition of a same TAG.

An embodiment of this application provides a method for determining a TAeffective time. A time interval N before the TA effective time isdetermined, and it is ensured that for a same terminal device, the timeinterval N is consistent when a plurality of UL subcarrier spacings areincluded. In this way, in a same TAG, TA effective times of the terminaldevice are consistent, so that uplink timing synchronization between theterminal device and the network device can be ensured.

FIG. 5 is a schematic flowchart of a method for determining an effectivemoment of a TA according to an embodiment of this application. Themethod 500 includes the following steps.

S510. A terminal device determines a first subcarrier spacing from Msubcarrier spacings, where the M subcarrier spacings are subcarrierspacings corresponding to L carriers used by a terminal device, andL≥M≥2.

Optionally, the first subcarrier spacing is a minimum subcarrier spacingamong the M subcarrier spacings, or the first subcarrier spacing is amaximum subcarrier spacing among the M subcarrier spacings.

It should be understood that the first subcarrier spacing may bedetermined based on one or more of a maximum/minimum value among alluplink subcarrier spacings, or a maximum/minimum value among subcarrierspacings of all bandwidth parts (BWP) in an active state, or amaximum/minimum value among subcarrier spacings of a plurality of BWPsconfigured for the terminal device, or a maximum/minimum value amongsubcarrier spacings of all BWPs. Alternatively, the first subcarrierspacing may be fixedly set to a subcarrier spacing, for example, for alow frequency (a working frequency that is less than or equal to 6 GHz),the first subcarrier spacing may be fixedly set to 15 kHz. Thisembodiment of this application includes these but is not limitedthereto.

In this embodiment of this application, one terminal device is used asan example for description. It is assumed that a network deviceconfigures L uplink carrier resources for a terminal device #A, and eachof the L uplink carrier resources has one subcarrier spacing, that is,the L uplink carrier resources have a total of M subcarrier spacings.Two or more of the L uplink carrier resources may have a same subcarrierspacing. Currently, in carrier resources, different subcarrier spacingsinclude 15 kHz, 30 kHz, 60 kHz, and 120 kHz, and may have morepossibilities in the future. It should be understood that thisapplication includes these subcarrier spacings but is not limitedthereto.

For example, if the network device configures four uplink carrierresources for the terminal device #A, the four uplink carrier resourcesmay have only one type of subcarrier spacing, for example, a subcarrierspacing of each of the four uplink carrier resources is 15 kHz; or thefour uplink carrier resources may have two types of subcarrier spacings,for example, a subcarrier spacing of one of the four uplink carrierresources is 15 kHz, and subcarrier spacings of the other three uplinkcarrier resources are 30 kHz; or the four uplink carrier resources mayhave three types of subcarrier spacings, for example, a subcarrierspacing of one of the four uplink carrier resources is 15 kHz, asubcarrier spacing of another one of the four uplink carrier resourcesis 30 kHz, and subcarrier spacings of the other two uplink carrierresources are 60 kHz; or the four uplink carrier resources may have fourtypes of subcarrier spacings, for example, a subcarrier spacing of oneof the four uplink carrier resources is 15 kHz, a subcarrier spacing ofanother one of the four uplink carrier resources is 30 kHz, a subcarrierspacing of still another one of the four uplink carrier resources is 60kHz, and a subcarrier spacing of the other UL carrier is 120 kHz. Theforegoing enumeration is merely a possible case and is merely used todescribe a possible relationship between a subcarrier spacing and acarrier resource. It should be understood that this application includesthis case but is not limited thereto.

It can be learned from the foregoing enumeration that a relationshipbetween L and M may be that a quantity L of carrier resources is greaterthan or equal to a quantity M of subcarrier spacings. Herein, it islimited that L M 2, and this is mainly because when the network deviceconfigures one carrier resource for the terminal device, the one carrierresource certainly has only one subcarrier spacing, for example, asubcarrier spacing of 15 kHz. In this case, in a process of calculatinga first time interval, because N₁, N₂, and TA_(max) are determined basedon the subcarrier spacing of 15 kHz and then respectively based on Table1, Table 2, and Table 3, a problem that TA effective times of differentUL carriers are different does not occur. Therefore, in thisapplication, M may be a positive integer greater than or equal to 2.

Optionally, when the first time interval N is calculated based on thequantity of subcarrier spacings, a subcarrier spacing of a carrierresource of a downlink signal is used as a reference.

Optionally, the first time interval may be determined with reference toa maximum subcarrier spacing or a minimum subcarrier spacing. Forexample, if the maximum subcarrier spacing is 30 kHz, and the minimumsubcarrier spacing is 15 kHz, the first time interval determinedaccording to the foregoing method is 5 ms. When the first time intervalis determined with reference to the subcarrier spacing of 15 kHz, 5 msis equivalent to 5 slots. To be specific, for an uplink carrier of 15kHz, a TA is applied starting from a sixth slot. When the first timeinterval is determined with reference to the subcarrier spacing of 30kHz, 5 ms is equivalent to 10 slots. To be specific, for an uplinkcarrier of 30 kHz, a TA is applied starting from an eleventh slot.

Optionally, when the first time interval is determined with reference tothe maximum subcarrier spacing, for a small subcarrier spacing, thefirst time interval cannot be integral slots, and a rounding upoperation needs to be performed on the first time interval. The roundingup operation means selecting a value that is greater than the originalfirst time interval and that is a minimum integer multiple of slotduration corresponding to the minimum subcarrier spacing. For example,the first time interval determined according to the foregoing method is2.5 ms, and includes two carriers (15 kHz and 30 kHz). Because 2.5 ms isnot an integer multiple of a slot corresponding to the subcarrierspacing of 15 kHz, the first time interval of 2.5 ms needs to be roundedup first based on a step of 15 kHz, that is, 3 ms. 3 ms corresponds to 3slots (15 kHz) and 6 slots (30 kHz). Therefore, for the subcarrierspacing of 15 kHz, a new TA is applied starting from a fourth slot, andfor the subcarrier spacing of 30 kHz, a new TA is applied starting froma seventh slot.

Specifically, in a process of determining N₁, μ=min(μ_(DL), μ_(UL)),where μ_(DL) corresponds to a subcarrier spacing of a PDSCH, and μ_(UL)corresponds to a subcarrier spacing of a hybrid automatic repeat requestacknowledgement (HARQ-ACK) corresponding to uplink transmission. In aprocess of determining N₂, μ=min(μ_(DL), μ_(UL)), where μ_(DL) may be asubcarrier spacing of a PDCCH used for scheduling a PUSCH in downlink,and μ_(UL) corresponds to a subcarrier spacing used for sending a PUSCHin uplink. In a process of determining TA_(max), μ corresponds to asubcarrier spacing of an uplink PUSCH. It should be understood that,both the PDCCH and the PDSCH are collectively referred to as a downlinkcarrier resource DL, and generally correspond to only one type ofsubcarrier spacings. This application includes these but is not limitedthereto.

For example, when a subcarrier spacing of a downlink DL is 15 kHz, and asubcarrier spacing of an uplink (UL) is 30 kHz, μ=min(μ_(DL),μ_(UL))=min(15 kHz, 30 kHz)=15 kHz.

In S510, the terminal device determines the first subcarrier spacingfrom the M subcarrier spacings. Specific methods for determining thefirst subcarrier spacing are listed as follows:

Case 1

For the L uplink (UL) carriers, N₁ and N₂ are determined with referenceto a minimum UL subcarrier spacing. For example, if L=2 uplink (UL)carriers are configured for the UE, and subcarrier spacings arerespectively 15 kHz and 30 kHz, N₁ and N₂ are calculated based on 15kHz.

Case 2

For the L uplink (UL) carriers, N₁ and N₂ are determined with referenceto a maximum UL subcarrier spacing. For example, if L=2 uplink (UL)carriers are configured for the UE, and subcarrier spacings arerespectively 15 kHz and 30 kHz, N₁ and N₂ are calculated based on 30kHz.

Case 3

For the L uplink (UL) carriers, TA_(max) is determined with reference toa minimum UL subcarrier spacing. For example, if L=2 uplink (UL)carriers are configured for the UE, and subcarrier spacings arerespectively 15 kHz and 30 kHz, TA_(max) is calculated based on 15 kHz.

Case 4

For the L uplink (UL) carriers, TA_(max) is determined with reference toa maximum UL subcarrier spacing. For example, if L=2 uplink (UL)carriers are configured for the UE, and subcarrier spacings arerespectively 15 kHz and 30 kHz, TA_(max) is calculated based on 30 kHz.

Case 5

For the L uplink (UL) carriers, N₁, N₂, and TA_(max) are determined withreference to a minimum UL subcarrier spacing. For example, if L=2 uplink(UL) carriers are configured for the UE, and subcarrier spacings arerespectively 15 kHz and 30 kHz, a time interval is calculated based on15 kHz.

Case 6

For the L uplink (UL) carriers, N₁, N₂, and TA_(max) are determined withreference to a maximum UL subcarrier spacing. For example, if L=2 uplink(UL) carriers are configured for the UE, and subcarrier spacings arerespectively 15 kHz and 30 kHz, a time interval is calculated based on30 kHz.

Case 7

For the L uplink (UL) carriers, N₁ and N₂ are determined with referenceto a minimum UL subcarrier spacing, and TA_(max) is determined withreference to a maximum UL subcarrier spacing.

For example, if L=2 uplink (UL) carriers are configured for the UE, andsubcarrier spacings are respectively 15 kHz and 30 kHz, duringcalculation of a time interval, N₁ and N₂ are determined based on 15kHz, and TA_(max) is determined based on 30 kHz.

Case 8

For the L uplink (UL) carriers, N₁ and N₂ are determined with referenceto a maximum UL subcarrier spacing, and TA_(max) is determined withreference to a minimum UL subcarrier spacing.

For example, if L=2 uplink (UL) carriers are configured for the UE, andsubcarrier spacings are respectively 15 kHz and 30 kHz, duringcalculation of a time interval, N₁ and N₂ are determined based on 30kHz, and TA_(max) is determined based on 15 kHz.

Case 9

For the L uplink (UL) carriers, N₁ and N₂ are determined with referenceto a minimum UL subcarrier spacing, and TA_(max) is determined withreference to a minimum value in a subcarrier spacing in the uplink (UL)carriers and a subcarrier spacing of a carrier resource used to transmitan Msg3, that is, μ=min(Msg3 SCS, UL SCS).

Case 10

For the L uplink (UL) carriers and subcarrier spacings of T messages 3(Msg3) in a random access process, N1 and N2 are determined withreference to a minimum UL subcarrier spacing, and TA_(max) is determinedwith reference to a maximum/minimum subcarrier spacing, that is,μ=min(max(Msg3 SCSs), UL SCS), or μ=min(min(Msg3 SCSs), UL SCS).

For example, if a base station configures random access resources on theUL carrier and an SUL carrier, and subcarrier spacings of the Msg3 ofthe base station are respectively 15 kHz or 30 kHz, μ corresponding toTA_(max) is determined with reference to the minimum subcarrier spacing15 kHz, or μ is determined with reference to the maximum subcarrierspacing 30 kHz.

Optionally, the L uplink (UL) subcarrier spacings (UL SCSs) may be SCSsof all bandwidth parts in an active state, or subcarrier spacings of aplurality of BWPs configured for the terminal device, or subcarrierspacings of all BWPs.

It should be understood that, in a random access process, a subcarrierspacing of an uplink carrier resource for transmitting the Msg3 may be15 kHz. After the random access process is completed, the subcarrierspacing for transmitting the uplink resource may be reconfigured. Forexample, a subcarrier spacing of an allocated carrier resource may be 30kHz or 60 kHz. Therefore, in consideration of impact of random access,impact of the subcarrier spacing of the Msg3 is considered in a processof determining TA_(max) herein. In addition, because a plurality ofuplink carriers may each have a corresponding random access resource,all uplink carriers may correspond to different subcarrier spacings ofthe message 3. For example, an uplink (UL) carrier and a supplementaryuplink (SUL) carrier are configured for the UE. The message 3 may havetwo subcarrier spacings, for example, 15 kHz and 30 kHz respectively.Therefore, in the process of determining TA_(max), impact of a pluralityof subcarrier spacings of the Msg3 is also taken into consideration.

For example, an uplink (UL) subcarrier spacing used by the UE isdifferent from that of the Msg3. To support a maximum coverage range,TA_(max) needs to be a minimum value in the subcarrier spacing of theMsg3 and the configured UL subcarrier spacing (SCS). For example, if L=2uplink (UL) carriers are configured for the UE, subcarrier spacings arerespectively 60 kHz and 30 kHz, and in a random access process, asubcarrier spacing (SCS) of a carrier resource for transmitting the Msg3is 15 kHz, during calculation of a time interval, N₁ and N₂ aredetermined based on 30 kHz, and TA_(max) is determined based on 15 kHz.

Ten possible cases of the first subcarrier spacing used for determiningN₁, N₂, and TA_(max) are listed above. It should be understood that theforegoing cases are merely examples instead of limitations. In variousprocesses of determining the first subcarrier spacing, there may be morecases of combining the first subcarrier spacings used for determiningN₁, N₂, and TA_(max). This application includes these cases but is notlimited thereto.

Optionally, in a process of determining the first subcarrier spacing,the terminal device may set a first threshold, and determine the firstthreshold as the first subcarrier spacing, to participate in subsequentdetermining of the effective moment of the TA.

Optionally, the foregoing method provided in this application mayalternatively be used in combination with the prior art. For example, aminimum value is obtained from the determined first subcarrier spacingof the uplink carrier resource and a subcarrier spacing of a downlinkcarrier resource, to obtain a subcarrier spacing. Details are notdescribed herein. It should be understood that this application includesthese but is not limited thereto.

In conclusion, the method for determining the first subcarrier spacingprovided in this embodiment of this application is to ensure that for asame terminal device, the time interval N is consistent when a pluralityof UL subcarrier spacings are included. In this way, in a same TAG, TAeffective times of the terminal device are consistent, so that uplinktiming synchronization between the terminal device and the networkdevice can be ensured.

S520. The terminal device determines an effective moment of a timingadvance (TA) of each of the L carriers based on the first subcarrierspacing.

By using the method in S510, the terminal device determines the firstsubcarrier spacing, and may further determine the effective moment ofthe timing advance (TA) of each carrier.

Optionally, the terminal device determines, based on the firstsubcarrier spacing, a first time interval corresponding to a firstcarrier in the L carriers, where the first time interval is a timeinterval between a receiving moment of a downlink signal and aneffective moment of a TA; and then determines the effective moment ofthe timing advance (TA) of each of the L carriers based on the firsttime interval.

For example, when a subcarrier spacing of a downlink DL is 15 kHz, thesubcarrier spacing of the uplink (UL) carrier is 30 kHz, andμ=min(μ_(DL), μ_(UL))=min(15 kHz, 30 kHz)=15 kHz, it is learnedaccording to Formula (1) that the first time intervalN=ceil(N₁+N₂+L₂+TA_(max))=ceil(13 symbols+10 symbols+0.5 ms+2ms)=ceil(58 symbols)=5 ms.

Optionally, the terminal device determines first duration N₁ based onthe first subcarrier spacing, where the first duration is durationrequired for processing a downlink signal; and/or determines secondduration N₂ based on the first subcarrier spacing, where the secondduration is duration required for preparing an uplink signal; and/ordetermines third duration TA_(max) based on the first subcarrierspacing, where the third duration is maximum duration that is allowed tobe indicated by a 12-bit timing advance command (TAC) when the thirdduration is determined based on the first subcarrier spacing. Theterminal device determines the first time interval based on one or moreof the first duration N₁, the second duration N₂, and the third durationTA_(max). It should be understood that a value of 12 bits herein ismerely an example instead of a limitation, and another possible valueless than 12 bits, for example, 6 bits, may also be used.

Optionally, the first time interval further includes fourth duration,and the fourth duration is duration determined by the terminal devicebased on a cell reuse mode, and/or the fourth duration is durationdetermined by the terminal device based on a frequency range withinwhich the terminal device or the network device works. For example, thefourth duration may be duration in which the terminal device performshandover in different working modes or working frequency bands. Fordetails about the fourth duration, refer to the foregoing relateddescriptions. The details are not described herein again. It should beunderstood that the duration required for processing a downlink signalis related to a downlink signal configuration such as a demodulationreference signal configuration, and/or a downlink signal subcarrierspacing, and/or a UE processing capability. It should be understood thatthe duration required for preparing an uplink signal is related to anuplink signal subcarrier spacing and/or a UE processing capability.

It should be understood that in the listed processes of determining thefirst time interval herein, a sum may be obtained according to Formula(1) by separately determining duration of N₁, N₂, L₂, and TA_(max), toobtain the first time interval N. Alternatively, in this embodiment ofthis application, only duration of one or more of N₁, N₂, L₂, andTA_(max) may be determined. In a technology development process, onlyduration of at least one of N₁, N₂, L₂, and TA_(max) needs to bedetermined, and the first time interval N may be obtained by using aspecific relationship. Herein, a method for determining duration of anyone or more of N₁, N₂, L₂, and TA_(max) by using the method provided inthis application falls within the protection scope of this application.

Specifically, examples of determining the first time interval N thatcorrespond to the listed ten cases are listed as follows:

Case 1

For the L uplink (UL) carriers, N₁ and N₂ are determined with referenceto a minimum UL subcarrier spacing. For example, if L=2 uplink (UL)carriers are configured for the UE, and subcarrier spacings arerespectively 15 kHz and 30 kHz, N₁ and N₂ are calculated based on 15kHz. N₁=13 symbols, and N₂=10 symbols.

Case 2

For the L uplink (UL) carriers, N₁ and N₂ are determined with referenceto a maximum UL subcarrier spacing. For example, if L=2 uplink (UL)carriers are configured for the UE, and subcarrier spacings arerespectively 15 kHz and 30 kHz, N₁ and N₂ are calculated based on 30kHz. N₁=13 symbols, and N₂=12 symbols.

Case 3

For the L uplink (UL) carriers, TA_(max) is determined with reference toa minimum UL subcarrier spacing. For example, if L=2 uplink (UL)carriers are configured for the UE, and subcarrier spacings arerespectively 15 kHz and 30 kHz, TA_(max) is calculated based on 15 kHz.TA_(max)=2 ms.

Case 4

For the L uplink (UL) carriers, TA_(max) is determined with reference toa maximum UL subcarrier spacing. For example, if L=2 uplink (UL)carriers are configured for the UE, and subcarrier spacings arerespectively 15 kHz and 30 kHz, TA_(max) is calculated based on 30 kHz.TA_(max)=1 ms.

Case 5

For the L uplink (UL) carriers, N₁, N₂, and TA_(max) are determined withreference to a minimum UL subcarrier spacing. For example, if L=2 uplink(UL) carriers are configured for the UE, and subcarrier spacings arerespectively 15 kHz and 30 kHz, a time interval is calculated based on15 kHz. For an uplink (UL) carrier whose subcarrier spacings are 15 kHzand 30 kHz, a first time interval N=ceil(N₁+N₂+TA_(max))=ceil(13symbols+10 symbols+0.5 ms+2 ms)=ceil(58 symbols)=5 ms.

Case 6

For the L uplink (UL) carriers, N₁, N₂, and TA_(max) are determined withreference to a maximum UL subcarrier spacing. For example, if L=2 uplink(UL) carriers are configured for the UE, and subcarrier spacings arerespectively 15 kHz and 30 kHz, a time interval is calculated based on30 kHz. For an uplink (UL) carrier whose subcarrier spacings are 15 kHzand 30 kHz, a first time interval N=ceil(N₁+N₂+TA_(max))=ceil(13symbols+12 symbols+0.5 ms+1 ms)=ceil(67 symbols)=2.5 ms.

Case 7

For the L uplink (UL) carriers, N₁ and N₂ are determined with referenceto a minimum UL subcarrier spacing, and TA_(max) is determined withreference to a maximum UL subcarrier spacing.

For example, if L=2 uplink (UL) carriers are configured for the UE, andsubcarrier spacings are respectively 15 kHz and 30 kHz, duringcalculation of a time interval, N₁ and N₂ are determined based on 15kHz, and TA_(max) is determined based on 30 kHz. For an uplink (UL)carrier whose subcarrier spacings are 15 kHz and 30 kHz, a first timeinterval N=ceil(N₁+N₂+L₂+TA_(max))=ceil(13 symbols+10 symbols+0.5 ms+1ms)=ceil(44 symbols)=4 ms.

Case 8

For the L uplink (UL) carriers, N₁ and N₂ are determined with referenceto a maximum UL subcarrier spacing, and TA_(max) is determined withreference to a minimum UL subcarrier spacing.

For example, if L=2 uplink (UL) carriers are configured for the UE, andsubcarrier spacings are respectively 15 kHz and 30 kHz, duringcalculation of a time interval, N₁ and N₂ are determined based on 30kHz, and TA_(max) is determined based on 15 kHz. For an uplink (UL)carrier whose subcarrier spacings are 15 kHz and 30 kHz, a first timeinterval N=ceil(N₁+N₂+L₂+TA_(max))=ceil(13 symbols+12 symbols+0.5 ms+2ms)=ceil(60 symbols)=5 ms.

Case 9

For the L uplink (UL) carriers, N₁ and N₂ are determined with referenceto a minimum UL subcarrier spacing, and TA_(max) is determined withreference to a minimum value in a subcarrier spacing in the uplink (UL)carriers and a subcarrier spacing of a carrier resource used to transmitan Msg3, that is, μ=min(Msg3 SCS, UL SCS).

Case 10

For the L uplink (UL) carriers and subcarrier spacings of M messages 3(Msg3) in a random access process, N1 and N2 are determined withreference to a minimum subcarrier spacing, and TA_(max) is determinedwith reference to a maximum/minimum subcarrier spacing, that is,μ=min(max(Msg3 SCSs), UL SCS), or μ=min(min(Msg3 SCSs), UL SCS).

For example, if the base station configures random access resources onthe UL and an SUL, and subcarrier spacings of the messages 3 of the basestation are respectively 15 kHz or 30 kHz, μ corresponding to TA_(max)is determined with reference to the minimum subcarrier spacing 15 kHz,or μ is determined with reference to the maximum subcarrier spacing 30kHz.

Optionally, the L uplink subcarrier spacings (UL SCSs) may be SCSs ofall bandwidth parts BWPs in an active state, or subcarrier spacings of aplurality of BWPs configured for the terminal device, or subcarrierspacings of all BWPs.

It should be understood that, in a random access process, a subcarrierspacing of an uplink carrier resource for transmitting the Msg3 may be15 kHz. After the random access process is completed, the subcarrierspacing for transmitting the uplink resource may be reconfigured. Forexample, a subcarrier spacing of an allocated carrier resource may be 30kHz or 60 kHz. Therefore, in consideration of impact of random access,impact of the subcarrier spacing of the Msg3 is considered in a processof determining TA_(max) herein. In addition, because a plurality ofuplink carriers may each have a corresponding random access resource,the uplink carriers may correspond to different subcarrier spacings ofthe message 3. For example, an uplink carrier UL and an SUL areconfigured for the UE. The message 3 may have two subcarrier spacings,for example, 15 kHz and 30 kHz respectively. Therefore, in the processof determining TA_(max), impact of a plurality of subcarrier spacings ofthe Msg3 is also taken into consideration.

For example, an uplink (UL) subcarrier spacing used by the UE isdifferent from that of the Msg3. To support a maximum coverage range,TA_(max) needs to be a minimum value in the subcarrier spacing of theMsg3 and the configured UL subcarrier spacing (SCS). For example, if L=2uplink (UL) carriers are configured for the UE, subcarrier spacings arerespectively 60 kHz and 30 kHz, and in a random access process, asubcarrier spacing (SCS) of a carrier resource for transmitting the Msg3is 15 kHz, during calculation of a time interval, N₁ and N₂ aredetermined based on 30 kHz, and TA_(max) is determined based on 15 kHz.When a subcarrier spacing (SCS) of a downlink UL is 15 kHz, for anuplink (UL) carrier whose subcarrier spacings are 30 kHz and 60 kHz, afirst time interval N=ceil(N₁+N₂+TA_(max))=ceil(13 symbols+12symbols+0.5 ms+2 ms)=ceil(60 symbols)=5 ms.

The foregoing enumerates ten possible cases of determining the firsttime interval based on the first subcarrier spacing. It should beunderstood that the foregoing cases are merely examples instead oflimitations. This application includes these cases but is not limitedthereto.

Optionally, in another possible implementation, the terminal devicedetermines a first mapping relationship, where the first mappingrelationship includes a one-to-one mapping relationship between aplurality of subcarrier spacing and a plurality of pieces of duration.The terminal device determines, based on the first mapping relationship,a first time interval corresponding to the first subcarrier spacing, andthen determines the effective moment of the timing advance (TA) of eachof the L carriers based on the first time interval.

Specifically, the terminal device learns, based on a network deviceconfiguration, subcarrier spacings of all uplink (UL) carriers in a TAG;and then, receives a MAC-CE that includes a TA adjustment command andthat is delivered by the network device, and determines an effectivemoment of a TA; and then, can use a new TA included in the MAC-CE.

After receiving the MAC-CE that includes TA adjustment, the terminaldevice determines the first time interval based on a minimum or maximumuplink subcarrier spacing in a same TAG. For example, the terminaldevice may determine the first time interval based on a preset functionin Table 6.

TABLE 6 Subcarrier spacing First time interval (unit: kHz) (unit: ms) 15 6 + n  30   3 + 0.5n  60  2.25 + 0.25n 120   1.5 + 0.125n

A value set of the integer n may be {−6, −5, −4, −3, −2, −1, 0, 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12}.

Optionally, a slot quantity equivalent to the first time interval inTable 4 may be used to represent the first time interval N, as shown inTable 7.

TABLE 7 Subcarrier spacing Effective time interval (unit: kHz) (unit:slot)  15  6 + n  30  6 + n  60  9 + n 120 12 + n

A value set of the integer n may be {−6, −5, −4, −3, −2, −1, 0, 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12}.

The foregoing describes a detailed process in which the terminal devicedetermines the effective moment of the timing advance (TA). Afterdetermining the first time interval N, the terminal device can determinethe effective moment of the TA by adding duration represented by thefirst time interval N to the receiving moment of the downlink signal.After determining the effective moment of the timing advance (TA) ofeach of the L carriers, the terminal device may send the uplinkinformation based on the timing advance (TA).

The UE may send uplink data according to the method shown in FIG. 3. Forexample, the UE may determine a downlink radio frame i based on areceived downlink radio frame i-1, and determine, based on a timingadvance T_(TA), that a start moment of an uplink radio frame i isT_(o)−T_(TA), where T_(o) is a start moment at which the UE receives thedownlink radio frame i. The UE may determine, based on the start momentof the uplink radio frame i, a time for sending uplink information. Thetime in which the UE sends the uplink information may be a part of timein the uplink radio frame.

The foregoing describes in detail the method for determining aneffective moment of a TA provided in this application with reference toFIG. 2 to FIG. 5. It may be understood that, to achieve the foregoingfunctions, a terminal device includes corresponding hardware structuresand/or software modules for performing the functions. The followingdescribes a communications apparatus in the embodiments of thisapplication in detail with reference to FIG. 6 to FIG. 8. FIG. 6 is aschematic block diagram of a communications apparatus 600 according toan embodiment of this application. The communications apparatus 600 maycorrespond to (for example, may be configured on or may be) the terminaldevice described in the method 500. When an integrated unit is used,FIG. 6 is a schematic diagram of a possible structure of the terminaldevice in the foregoing embodiments. The terminal device 600 includes adetermining unit 610 and a sending unit 620.

In a possible design, the communications apparatus 600 may be a terminaldevice or a chip configured in the terminal device.

The determining unit 610 is configured to determine a first subcarrierspacing from M subcarrier spacings, where the M subcarrier spacings aresubcarrier spacings corresponding to L carriers used by a terminaldevice, and L≥M≥2.

The determining unit 610 is further configured to determine an effectivemoment of a timing advance (TA) of each of the L carriers based on thefirst subcarrier spacing.

Optionally, the determining unit 610 is further configured to:determine, based on the first subcarrier spacing, a first time intervalcorresponding to a first carrier in the L carriers, where the first timeinterval is a time interval between a receiving moment of a downlinksignal and an effective moment of a TA; and determine the effectivemoment of the timing advance (TA) of each of the L carriers based on thefirst time interval.

Optionally, the determining unit 610 is further configured to: determinefirst duration based on the first subcarrier spacing, where the firstduration is duration required for processing a downlink signal; and/ordetermine second duration based on the first subcarrier spacing, wherethe second duration is duration required for preparing an uplink signal;and/or determine third duration based on the first subcarrier spacing,where the third duration is maximum duration that is allowed to beindicated by a 12-bit timing advance command (TAC) when the thirdduration is determined based on the first subcarrier spacing. Thedetermining unit 610 determines the first time interval based on one ormore of the first duration, the second duration, and the third duration.

Optionally, the first time interval further includes fourth duration,and the fourth duration is duration determined by the terminal devicebased on a cell reuse mode, and/or the fourth duration is durationdetermined by the terminal device based on a frequency range withinwhich the terminal device or a network device works. For example, thefourth duration is duration in which the terminal device performshandover in different working modes or working frequency bands. Fordetails about the fourth duration, refer to the foregoing relateddescriptions. The details are not described herein again.

Optionally, the determining unit 610 is further configured to: determinea first mapping relationship, where the first mapping relationshipincludes a one-to-one mapping relationship between a plurality ofsubcarrier spacing and a plurality of pieces of duration; determine,based on the first mapping relationship, a first time intervalcorresponding to the first subcarrier spacing; and determine theeffective moment of the timing advance (TA) of each of the L carriersbased on the first time interval.

Optionally, the first subcarrier spacing is a minimum subcarrier spacingamong the M subcarrier spacings, or the first subcarrier spacing is amaximum subcarrier spacing among the M subcarrier spacings.

It should be understood that the first subcarrier spacing may bedetermined based on one or more of a maximum/minimum value among alluplink subcarrier spacings, or a maximum/minimum value among subcarrierspacings of all BWPs in an active state, or a maximum/minimum valueamong subcarrier spacings of a plurality of BWPs configured for theterminal device, or a maximum/minimum value among subcarrier spacings ofall BWPs. Alternatively, the first subcarrier spacing may be fixedly setto a subcarrier spacing, for example, for a low frequency (a workingfrequency that is less than or equal to 6 GHz), the first subcarrierspacing may be fixedly set to 15 kHz.

Optionally, the apparatus 600 further includes the sending unit 620,configured to send uplink information based on the timing advance (TA).

It should be understood that the communications apparatus 600 maycorrespond to the terminal device in the communication method 200 andthe terminal device in the communication method 500 according to theembodiments of this application, and the communications apparatus 600may include modules configured to perform the methods performed by theterminal device in the communication method 200 in FIG. 2 and thecommunication method 500. In addition, the modules in the communicationsapparatus 600 and the foregoing other operations and/or functions areseparately used to implement corresponding procedures in thecommunication method 200 in FIG. 2 and the communication method 500. Forbrevity, details are not described herein again.

FIG. 7 is a schematic structural diagram of a terminal device 700according to an embodiment of this application. As shown in FIG. 7, theterminal device 700 includes a processor 710 and a transceiver 720.Optionally, the terminal device 700 further includes a memory 730. Theprocessor 710, the transceiver 720, and the memory 730 communicate witheach other by using an internal connection path to transfer a controlsignal and/or a data signal. The memory 730 is configured to store acomputer program. The processor 710 is configured to invoke and run thecomputer program from the memory 730, to control the transceiver 720 toreceive or transmit a signal.

The processor 710 and the memory 730 may be integrated into a processingapparatus, and the processor 710 is configured to execute program codestored in the memory 730, to implement the foregoing functions. Inspecific implementation, the memory 730 may alternatively be integratedinto the processor 710, or may be independent of the processor 710.

The terminal device may further include an antenna 740, configured tosend, by using a radio signal, downlink data or downlink controlsignaling that is output by the transceiver 720.

FIG. 8 is a schematic structural diagram of a terminal device 800according to an embodiment of this application. As shown in FIG. 8, theterminal device 800 includes a processor 801 and a transceiver 802.Optionally, the terminal device 800 further includes a memory 803. Theprocessor 802, the transceiver 802, and the memory 803 communicate witheach other by using an internal connection path to transfer a controlsignal and/or a data signal. The memory 803 is configured to store acomputer program. The processor 801 is configured to invoke and run thecomputer program from the memory 803, to control the transceiver 802 toreceive or transmit a signal.

The processor 801 and the memory 803 may be integrated into a processingapparatus 804, and the processor 801 is configured to execute programcode stored in the memory 803, to implement the foregoing functions. Inspecific implementation, the memory 803 may alternatively be integratedinto the processor 801, or may be independent of the processor 801. Theterminal device 800 may further include an antenna 810, configured tosend, by using a radio signal, uplink data or uplink control signalingthat is output by the transceiver 802.

Specifically, the terminal device 800 may correspond to the terminaldevice in the communication method 200 and the communication method 500according to the embodiments of this application. The terminal device800 may include modules configured to perform the methods performed bythe terminal device in the communication method 200 in FIG. 2. Inaddition, the modules in the terminal device 800 and the foregoing otheroperations and/or functions are separately used to implementcorresponding procedures in the communication method 200 in FIG. 2 andthe communication method 500. For brevity, details are not describedherein again.

The processor 801 may be configured to execute the actions implementedinternally by the terminal device described in the foregoing methodembodiments, and the transceiver 802 may be configured to execute theactions of performing receiving or sending by the terminal devicedescribed in the foregoing method embodiments. For details, refer to thedescriptions in the foregoing method embodiments. The details are notdescribed herein again.

The processor 801 and the memory 803 may be integrated into a processingapparatus, and the processor 801 is configured to execute program codestored in the memory 803, to implement the foregoing functions. Inspecific implementation, the memory 803 may alternatively be integratedinto the processor 801.

The terminal device 800 may further include a power supply 805,configured to supply power to various components or circuits in theterminal device.

In addition, to improve functions of the terminal device, the terminaldevice 800 may further include one or more of an input unit 814, adisplay unit 816, an audio frequency circuit 818, a camera 82 o, asensor 822, and the like. The audio frequency circuit may furtherinclude a loudspeaker 882, a microphone 884, and the like.

It should be understood that, the terminal device in the foregoingapparatus embodiments completely correspond to the terminal device inthe method embodiments, and corresponding modules or units performcorresponding steps. For example, a sending module (transmitter)performs a sending step in the method embodiments, a receiving module(receiver) performs a receiving step in the method embodiments, andother steps other than the sending and receiving steps may be performedby a processing module (processor). For functions of specific modules,refer to a corresponding method embodiment. The sending module and thereceiving module may form a transceiver module, and the transmitter andthe receiver may form a transceiver, to jointly implement a transceiverfunction. There may be one or more processors.

A person of ordinary skill in the art may be aware that, in combinationwith the examples described in the embodiments disclosed in thisspecification, units and algorithm steps may be implemented byelectronic hardware or a combination of computer software and electronichardware. Whether the functions are performed by hardware or softwaredepends on particular applications and design constraints of thetechnical solutions. A person skilled in the art may use differentmethods to implement the described functions for each particularapplication, but it should not be considered that the implementationgoes beyond the scope of this application.

It may be clearly understood by a person skilled in the art that, forthe purpose of convenient and brief description, for a detailed workingprocess of the foregoing system, apparatus, and unit, refer to acorresponding process in the foregoing method embodiments, and detailsare not described herein again.

In the embodiments provided in this application, it should be understoodthat the disclosed system, apparatus, and method may be implemented inother manners. For example, the described apparatus embodiment is merelyan example. For example, the unit division is merely logical functiondivision and may be other division in actual implementation. Forexample, a plurality of units or components may be combined orintegrated into another system, or some features may be ignored or notperformed. In addition, the displayed or discussed mutual couplings ordirect couplings or communication connections may be implemented byusing some interfaces. The indirect couplings or communicationconnections between the apparatuses or units may be implemented inelectronic, mechanical, or other forms.

The units described as separate parts may or may not be physicallyseparate, and parts displayed as units may or may not be physical units,may be located in one position, or may be distributed on a plurality ofnetwork units. Some or all of the units may be selected based on actualrequirements to achieve the objectives of the solutions of theembodiments.

In addition, functional units in the embodiments of this application maybe integrated into one processing unit, or each of the units may existalone physically, or two or more units are integrated into one unit.

When the functions are implemented in the form of a software functionalunit and sold or used as an independent product, the functions may bestored in a computer readable storage medium. Based on such anunderstanding, the technical solutions of this application essentially,or the part contributing to the prior art, or some of the technicalsolutions may be implemented in a form of a software product. Thesoftware product is stored in a storage medium, and includes severalinstructions for instructing a computer device (which may be a personalcomputer, a server, or a network device) to perform all or some of thesteps of the methods described in the embodiments of this application.The foregoing storage medium includes any medium that can store programcode, such as a USB flash drive, a removable hard disk, a read-onlymemory (ROM), a random access memory (RAM), a magnetic disk, or anoptical disc.

The foregoing descriptions are merely specific implementations of thisapplication, but are not intended to limit the protection scope of thisapplication. Any variation or replacement readily figured out by aperson skilled in the art within the technical scope disclosed in thisapplication shall fall within the protection scope of this application.Therefore, the protection scope of this application shall be subject tothe protection scope of the claims.

What is claimed is:
 1. A communication method, comprising: receiving, bya terminal device, a timing advance (TA) adjustment command; anddetermining, by the terminal device, an effective time of an adjustedtiming advance (TA) based on subcarrier spacings of more than onecarrier, the effective time of the adjusted TA being a time at which theterminal device starts using the adjusted TA for uplink transmissionsafter receiving the TA adjustment command; and wherein determining theeffective time comprises: determining, by the terminal device, aneffective slot of the adjusted TA based on a first duration, a secondduration, or a third duration, wherein the first duration, the secondduration, or the third duration is associated with one of the subcarrierspacings of the more than one carrier; and wherein that the firstduration, the second duration, or the third duration is associated withone of the subcarrier spacings of the more than one carrier comprises:the third duration is associated with a second subcarrier spacing,wherein the second subcarrier spacing is a minimum subcarrier spacing ina subcarrier spacing of a carrier used to transmit a message 3 (Msg3)and a subcarrier spacing of an uplink carrier configured for theterminal device, and the third duration is a maximum duration that isindicatable by a timing advance command (TAC).
 2. The method accordingto claim 1, wherein the first duration is a duration for processing adownlink signal by the terminal device, the second duration is aduration for preparing an uplink signal by the terminal device, and thethird duration is a maximum duration that is indicated by a 6-bit or12-bit timing advance command (TAC).
 3. The method according to claim 1,wherein that the first duration, the second duration, or the thirdduration is associated with one of the subcarrier spacings of the morethan one carrier comprises: the first duration or the second duration isassociated with a first subcarrier spacing, wherein the first subcarrierspacing is a minimum subcarrier spacing in the subcarrier spacings ofthe more than one carrier, wherein the first duration is a duration forprocessing a downlink signal, and the second duration is a duration forpreparing an uplink signal.
 4. The method according to claim 3, furthercomprising: predefining a correspondence between a plurality ofsubcarrier spacings and respective first durations, and between theplurality of subcarrier spacings and respective second durations, thefirst subcarrier spacing being one of the plurality of subcarrierspacings.
 5. The method according to claim 1, wherein the carrier usedto transmit the Msg3 comprises a carrier that is used to transmit theMsg3 when an uplink carrier and a supplementary uplink carrier areconfigured for the terminal device.
 6. The method according to claim 1,further comprising: predefining a correspondence between a plurality ofsubcarrier spacings and respective third durations, the secondsubcarrier spacing being one of the plurality of subcarrier spacings. 7.The method according to claim 1, wherein the more than one carriercomprise an uplink carrier and a downlink carrier.
 8. The methodaccording to claim 1, wherein the effective time belongs to a timingadvance group (TAG).
 9. A communications apparatus, comprising: areceiver, configured to receive a timing advance (TA) adjustmentcommand; and a processor, configured to determine an effective time ofan adjusted timing advance (TA) based on subcarrier spacings of morethan one carrier, the effective time of the adjusted TA being a time atwhich the communications apparatus starts using the adjusted TA foruplink transmissions after receiving the TA adjustment command; andwherein determining the effective time comprises: determining aneffective slot of the adjusted TA based on a first duration, a secondduration, or a third duration, wherein the first duration, the secondduration, or the third duration is associated with one of the subcarrierspacings of the more than one carrier; and wherein that the firstduration, the second duration, or the third duration is associated withone of the subcarrier spacings of the more than one carrier comprises:the third duration is associated with a second subcarrier spacing,wherein the second subcarrier spacing is a minimum subcarrier spacing ina subcarrier spacing of a carrier used to transmit a message 3 (Msg3)and a subcarrier spacing of an uplink carrier configured for thecommunications apparatus, and the third duration is a maximum durationthat is indicatable by a timing advance command (TAC).
 10. Thecommunications apparatus according to claim 9, wherein the firstduration is a duration for processing a downlink signal by thecommunications apparatus, the second duration is a duration forpreparing an uplink signal by the communications apparatus, and thethird duration is a maximum duration that is indicated by a 6-bit or12-bit timing advance command (TAC).
 11. The communications apparatusaccording to claim 9, wherein that the first duration, the secondduration, or the third duration is associated with one of the subcarrierspacings of the more than one carrier comprises: the first duration orthe second duration is associated with a first subcarrier spacing,wherein the first subcarrier spacing is a minimum subcarrier spacing inthe subcarrier spacings of the more than one carrier, wherein the firstduration is a duration for processing a downlink signal by thecommunications apparatus, and the second duration is a duration forpreparing an uplink signal by the communications apparatus.
 12. Thecommunications apparatus according to claim 11, wherein the processor isfurther configured to: predefine a correspondence between a plurality ofsubcarrier spacings and respective first durations, and between theplurality of subcarrier spacings and respective second durations, thefirst subcarrier spacing being one of the plurality of subcarrierspacings.
 13. The communications apparatus according to claim 9, whereinthe carrier used to transmit the Msg3 comprises a carrier that is usedto transmit the Msg3 when an uplink carrier and a supplementary uplinkcarrier are configured for the communications apparatus.
 14. Thecommunications apparatus according to claim 9, wherein the processor isfurther configured to: predefine a correspondence between a plurality ofsubcarrier spacings and respective third durations, the secondsubcarrier spacing being one of the plurality of subcarrier spacings.15. The communications apparatus according to claim 9, wherein the morethan one carrier comprise an uplink carrier and a downlink carrier. 16.The communications apparatus according to claim 9, wherein the effectivetime belongs to a timing advance group (TAG).
 17. The method accordingto claim 1, wherein the subcarrier spacing of the uplink carrierconfigured for the terminal device is a subcarrier spacing of abandwidth part (BWP) configured for the terminal device.
 18. Thecommunications apparatus according to claim 9, wherein the subcarrierspacing of the uplink carrier configured for the communicationsapparatus is a subcarrier spacing of a bandwidth part (BWP) configuredfor the communications apparatus.